Differential regulation of proliferation and neuronal differentiation in adult rat spinal cord neural stem/progenitors by ERK1/2, Akt, and PLCγ

Abstract

Proliferation of endogenous neural stem/progenitor cells (NSPCs) has been identified in both normal and injured adult mammalian spinal cord. Yet the signaling mechanisms underlying the regulation of adult spinal cord NSPCs proliferation and commitment toward a neuronal lineage remain undefined. In this study, the role of three growth factor-mediated signaling pathways in proliferation and neuronal differentiation was examined. Adult spinal cord NSPCs were enriched in the presence of fibroblast growth factor 2 (FGF2). We observed an increase in the number of cells expressing the microtubule-associated protein 2 (MAP2) over time, indicating neuronal differentiation in the culture. Inhibition of the mitogen-activated protein kinase or extracellular signal-regulated kinase (ERK) kinase 1 and 2/ERK 1 and 2 (MEK/ERK1/2) or the phosphoinositide 3-kinase (PI3K)/Akt pathways suppressed active proliferation in adult spinal cord NSPC cultures; whereas neuronal differentiation was negatively affected only when the ERK1/2 pathway was inhibited. Inhibition of the phospholipase Cγ (PLCγ) pathway did not affect proliferation or neuronal differentiation. Finally, we demonstrated that the blockade of either the ERK1/2 or PLCγ signaling pathways reduced neurite branching of MAP2+ cells derived from the NSPC cultures. Many of the MAP2+ cells expressed synaptophysin and had a glutamatergic phenotype, indicating that over time adult spinal cord NSPCs had differentiated into mostly glutamatergic neurons. Our work provides new information regarding the contribution of these pathways to the proliferation and neuronal differentiation of NSPCs derived from adult spinal cord cultures, and emphasizes that the contribution of these pathways is dependent on the origin of the NSPCs.

Substance P stimulates proliferation of spinal neural stem cells in spinal cord injury via the mitogen-activated protein kinase signaling pathway

“…Substance P activates the MAP kinase signaling pathway [24,25], and this pathway has been shown to be involved in regulating proliferation and self-renewal of NSPCs [26,27]. Our data suggest that the stimulatory effect of SP on NSPCs is mediated by ERKs and p38 MAP kinases.…”

“…The FGF2 stimulates the proliferation of rat NSPCs by an ERK-mediated mechanism [52], and FGF2 maintains mouse cortical NSPCs in a proliferative state by a mechanism involving ERK-mediated upregulation of gap junctions [53]. Recently, Chan et al [26] demonstrated that proliferation of NSPC in adult rat SC-NSPCs was regulated by ERK MAP kinase. Also, the p38 MAP kinase promotes differentiation of mouse NSPCs [54] and mediates the proliferative effects of FGF2 and the platelet-derived growth factor on oligodendrocyte progenitor cells [55].…”

“…However, we could not find any experimental study that investigates SP action in the spinal cord. Substance P activates the mitogen-activated protein (MAP) kinase signaling pathway [24,25], and this pathway has been shown to be involved in regulating the proliferation and self-renewal of NSPCs [26,27]. Based on these data, we hypothesized that SP has an important role in NSPC proliferation in the adult rat spinal cord, and its main mechanism is through the MAP kinase signaling pathway.…”

Inhibition of Protein Kinases AKT and ERK1/2 Reduce the Carotid Body Chemoreceptor Response to Hypoxia in Adult Rats

“…Besides, the pathways of protein kinase B (AKT) and extracellular signal-regulated kinases ½ (ERK1/2), are involved in major processes accomplishing a wide variety of neural tasks, including glucose metabolism (Engelman et al 2006 ), cellular apoptosis and survival (Teng et al 2014 ), differentiation (Chan et al 2013 ), neural proliferation and migration (Dey et al 2005 ), neuro-protection (Zhang et al 2014 ), neuro-degeneration (Fang et al 2014 ), and synaptic signaling (Yoshii and Constantine-Paton 2014 . Moreover, AKT and ERK1/2 in brain tissue participate in the modulation of dopaminergic (Beaulieu et al 2006 ), muscarinic (Rosenblum et al 2000 ), adrenergic (Taraviras et al 2002 ), serotonergic (Cowen 2007 ), GABAergic (Balasubramanian et al 2004 ) and adenosinergic (Wiese et al 2007 ) neurotransmission.…”

Valproic Acid Arrests Proliferation but Promotes Neuronal Differentiation of Adult Spinal NSPCs from SCI Rats

“…Primary culture of adult rat spinal cord-derived NSPCs was performed as described previously, with slight modifications [24,25]. At day 15 after compressive SCI, the rats were anesthetized and perfused with artificial cerebrospinal fluid.…”